Two major bodies representing footballers and football clubs in Europe are filing a complaint to the European Commission accusing Fifa of abusing its position.
Football's world governing body has taken "unilateral decisions" and its conduct "infringes EU competition law and notably constitutes an abuse of dominance", FIFPro Europe and the European Leagues body said in a statement on Tuesday.
FIFPro is the global players' union while European Leagues brings together more than one thousand clubs from 33 countries around Europe.
They say Fifa's conduct with regards to the international match calendar has "harmed the economic interests of national leagues and the welfare of players" and argue Fifa's role as a regulator and competition organiser is a conflict of interest.
Fifa has been accused of a failure to consult over recent changes to the calendar, such as the introduction of a 32-team Club World Cup.
The first edition of the expanded Club World Cup is set to take place in the United States in June and July next year and 12 European clubs are due to feature.
Many of the continent's leading players will therefore be obliged to participate at a time when they would otherwise have been afforded a long close-season break, a year ahead of the expanded 48-team World Cup in North America.
"The international match calendar is now beyond saturation and has become unsustainable for national leagues and a risk for the health of players," FIFPro and European Leagues said.
"Fifa's decisions over the last years have repeatedly favoured its own competitions and commercial interests, neglected its responsibilities as a governing body, and harmed the economic interests of national leagues and the welfare of players.
"National leagues and player unions, which represent the interests of all clubs and all players at the national level, and regulate labour relations through collectively agreed solutions, cannot accept that global regulations are decided unilaterally.
"Legal action is now the only responsible step for European leagues and player unions to protect football, its ecosystem and its workforce from Fifa's unilateral decisions."
FIFA'S CONDUCT 'FALLS SHORT'
The statement refers to the Super League judgement from the European Court of Justice last December, which required Fifa and other governing bodies to exercise their regulatory functions in a way that is transparent, objective, non-discriminatory and proportionate.
Fifa's conduct over the calendar, they allege, "falls well short of these requirements".
Spain's LaLiga, which is not a member of European Leagues, has also joined the complaint.
It comes after England's Professional Footballers' Association and their French counterparts, the UNFP, launched an action in the Belgian courts in June to ultimately determine whether Fifa's actions had breached players' rights under European Union law.